NHE9-Mediated pH Modulation and Liposome Rigidity as Determinants of Viral Cargo Motility

Understanding the intracellular transport of viruses is essential for the development of new antiviral strategies. In this study, we investigated how endosomal pH fluctuations, regulated by the Na⁺/H⁺ exchanger NHE9, influence motor protein activity during SARS-CoV-2 transport in cardiomyocytes. NHE9 has been identified as a COVID-19 risk factor and is thought to be upregulated by interferon responses. Previous work suggests that increased NHE9 expression disrupts endosome motility toward the cell center by reducing dynein activity while enhancing kinesin-driven peripheral transport.

Unlike rigid polystyrene beads, these artificial endosomes allowed us to directly probe how membrane composition and rigidity affect motor protein function. Liposomes with varying cholesterol content were synthesized to tune membrane stiffness.

Preliminary results indicate that liposomes display distinct mechanical behaviors compared to rigid beads, with increased membrane fluidity correlating with altered kinesin motility and reduced detachment forces. Together, these findings establish a framework for dissecting how endosomal pH, lipid membrane mechanics, and motor protein activity converge to regulate SARS-CoV-2 intracellular trafficking. This work highlights the importance of lipid cargo properties in viral transport and provides a platform for identifying potential antiviral intervention points.